JP6160827B2 - Optical coherence tomography device - Google Patents

Description

  Optical coherence tomography device for obtaining internal information of test object (for example, eye)

As one of optical coherence tomography (OCT), SS-OCT (Swept Source OCT) using a wavelength swept light source is known. SS-OCT is
The emission wavelength is temporally changed by the wavelength swept light source, and the spectrum including the reflected light from the test object and the reference light is detected by the photodetector. The spectrum signal output from the photodetector is converted into depth information through Fourier analysis.

  By the way, since the wavelength change by the wavelength swept light source is not necessarily proportional to time, the relationship between the wave number (K) and the depth (Z) may not necessarily be proportional in the Fourier transform process. As a result, for example, there is a possibility that an OCT signal including information whose original depth profile is broken may be acquired.

  As one of countermeasures, an interferometer different from the OCT interference optical system is provided, and mapping data relating to the wave number is generated (see Non-Patent Document 1). In SD-OCT, a gold mirror disposed in a measurement optical path is photographed a plurality of times, and mapping data relating to the wave number is generated from these signals (see Non-Patent Document 2).

“Ultra high-speed swept source OCT imaging of the anterior segment of human eye at 200 kHz with adjustable imaging range”, Michalina Gora, Optics Express, Vol. 17, No. 17 “Full-range, high-speed, high-resolution 1-μm spectral-domain optical coherence tomography using BM-scan for volumetric imaging of the human posterior eye”, Shuichi Makita, Optics Express, Vol. 16, No. 12

  However, the method of Non-Patent Document 1 requires another interferometer. Further, even if data creation using a gold mirror is used, it is necessary to acquire data at a time different from the original measurement, so that the influence of temporal fluctuations on the original measurement cannot be dealt with.

  An object of the present invention is to provide an optical coherence tomography apparatus that solves at least one of the above-mentioned drawbacks of the prior art.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1)
An SS-OCT optical system using a wavelength swept light source that temporally sweeps the emission wavelength is provided, and an interference signal between the measurement light and the reference light is sampled according to a change in the emission wavelength by the wavelength swept light source, and obtained by sampling. An optical coherence tomography device that obtains internal information of a test object based on interference signals at respective wavelengths,
An optical splitter that divides interference signal light generated by interference between the measurement light and the reference light into first interference signal light and second interference signal light having a phase difference with respect to the first interference signal light. When,
A first detector for detecting the first interference signal light; and a second detector for detecting the second interference signal light, the detection from the first detector and the second detector. A balanced detector for processing the signal for balanced detection;
A stationary pattern noise caused by either the first interference signal light or the second interference signal light is disposed between one of the first detector and the second detector and the optical splitter. An optical member for causing
Correction information for correcting the mapping state of the wave number component to each sampling point in the balanced detector is calculated based on the signal component corresponding to the stationary pattern noise included in the detection signal output from the balanced detector. Computing processing means to be obtained;
It is characterized by providing .

It is a figure for demonstrating the structure of the apparatus which concerns on the Example of this embodiment. It is the figure which showed the interference of the light beam which injected into the cover glass used for a calibration. It is the figure which showed typically the correction process of wave number mapping. It is a figure for demonstrating the structure of the apparatus which concerns on the modification 1 of this embodiment. It is a figure for demonstrating the structure of the apparatus which concerns on the modification 2 of this embodiment.

  An example of an embodiment of the present invention will be described with reference to the drawings. 1-5 is a figure which concerns on the Example of this embodiment.

<Overview>
The SS-OCT apparatus 1 of the present embodiment uses correction information for correcting the mapping state of the wave number component for each sampling point in the balanced detector 121 as stationary pattern noise included in the detection signal output from the balanced detector 121. Is obtained by calculation based on the signal component corresponding to. The obtained correction information is used when obtaining the internal information of the test object based on the interference signal for each wave number.

<Basic configuration>
The SS-OCT apparatus 1 has SS-OCT as a basic configuration. The SS-OCT apparatus 1 mainly includes an interference optical system 100 (OCT optical system) and an arithmetic controller (arithmetic processor) 70. The technique of this apparatus may be applied to, for example, a standard OCT for detecting the reflection intensity of a test object. Further, the present invention may also be applied to polarization sensitive OCT (PS-OCT) and Doppler OCT for detecting the phase state of a test object. Of course, the present invention may be applied to multi-function OCT in which PS-OCT and Doppler OCT are combined.

  As the interference optical system 100, an SS-OCT optical system using a wavelength swept light source (for example, the light source 102) that sweeps the emission wavelength with respect to time is used. The SS-OCT apparatus 1 samples, for example, an interference signal between the measurement light and the reference light according to a change in the emission wavelength by the wavelength swept light source, and a test object based on the interference signal at each wavelength obtained by the sampling. Get inside information.

  The interference optical system 100 has a configuration related to an interferometer for obtaining a tomographic image of a test object using the OCT principle. The interference optical system 100 includes a splitter (light splitter), a measurement light path, a reference light path, a combiner (light combiner), and a light detector (hereinafter, detector) 120. A splitter (eg, coupler 104) splits light from the wavelength swept light source into a measurement optical path and a reference optical path. For the splitter and combiner, for example, a beam splitter, a half mirror, a fiber coupler, a circulator, or the like is used. The measurement optical path has a configuration for guiding light to the test object. The reference optical path has a configuration for causing the light to travel in the apparatus and to interfere with the measurement light. The combiner combines (interferences) the measurement light from the measurement optical path reflected by the test object and the reference light from the reference optical path. The optical scanner 108 is disposed, for example, in the measurement optical path, and is used for scanning the measurement light on the test object.

  The optical splitter (for example, the beam splitter 350 and the coupler 450) converts the interference signal light generated by the interference between the measurement light and the reference light into a first interference signal light and a first interference signal having a phase difference with respect to the first interference signal. Divided into two interference signal lights. For example, the optical splitter is arranged in an optical path after a position where interference between the measurement light and the reference light occurs.

<Balance detector>
The detector 120 receives the interference signal light generated by the interference between the measurement light and the reference light. A balanced detector 121 is used for the detector 120 of the present embodiment. The balanced detector 121 includes a first detector 121a for detecting the first interference signal light and a second detector 121b for detecting the second interference signal light. The balanced detector 121 is used for performing balanced detection by processing detection signals from the first detector 121a and the second detector 121b.

<Pattern noise generating member>
Either the first interference signal light or the second interference signal light is provided between any one of the first detector 121a and the second detector 121b and the optical splitter (for example, the beam splitter 350 and the coupler 450). An optical member (for example, a cover glass 400) for generating a steady pattern noise due to is disposed. Such an optical member may be disposed, for example, such that each of the front surface and the rear surface of the optical member intersects perpendicularly to the optical axis.

  Note that the optical member as described above is disposed on the higher one of the first detector 121a and the second detector 121b in which the light splitting ratio by the light splitter (for example, the beam splitter 350 or the coupler 450) is higher. May be. In this case, the signal strength imbalance between the first detector 121a and the second detector 121b is reduced.

<Calculation processing>
The arithmetic controller 70 can execute at least one of control processing, image processing, and arithmetic processing of each component of the apparatus. For example, the arithmetic controller 70 obtains a detection signal from the detector 120. The arithmetic controller 70 obtains a spectrum signal including interference signal light at each wavelength, and processes the spectrum signal. The arithmetic controller 70 processes the spectrum signal to obtain internal information of the test object (for example, test object data (depth information) in the depth direction).

  Further, the arithmetic controller 70 may obtain information on the test object (for example, morphological information, polarization characteristics, etc.) by arranging internal information obtained at different positions by scanning the measurement light or the like. The arithmetic controller 70 stores the obtained result in the memory 72. The arithmetic controller 70 may display the obtained result on the monitor 75 (image display unit).

  The spectrum signal (spectrum data) is rewritten as a function of the wavelength λ and converted into a function I (k) that is equally spaced with respect to the wave number k (= 2π / λ). The arithmetic controller 70 obtains a signal distribution in the depth (Z) region by Fourier-transforming the spectrum signal in the wave number k space.

  In the present embodiment, the arithmetic controller 70 uses correction information for correcting the mapping state of the wave number component to each sampling point in the balanced detector 121 as stationary pattern noise included in the detection signal output from the balanced detector 121. It is obtained by calculation based on a signal component corresponding to (FPN: Fixed Pattern Noise).

  For example, the calculation controller 70 may correct the correspondence between each wavelength component and each sampling point using the obtained correction information, and obtain the internal information of the test object using the corrected correspondence. Note that the arithmetic controller 70 may acquire correction information for each spectrum signal acquired at a predetermined frame rate, for example, and may obtain internal information using the acquired correction information.

  Information after the Fourier transform is expressed as a signal including a real component and an imaginary component in the Z space. When obtaining the form information, the arithmetic controller 70 obtains an A scan signal (signal intensity value in the depth direction) by, for example, obtaining absolute values of real and imaginary components in the signal in the Z space. The arithmetic controller 70 can also obtain the tomographic image of the test object by arranging the A scan signals obtained at different positions.

  The test object may be a living body such as an eye (anterior eye portion, fundus oculi, etc.), skin, or a material other than the living body.

<Phase shift of spectrum signal>
The arithmetic controller 70 may correct the phase shift of the spectrum signal including the interference signal at each wavelength, for example, using the steady pattern noise generated by the pattern noise generating member. After correcting the phase shift, the arithmetic controller 70 may correct the wave number component mapping state for each sampling point as described above.

  For example, regarding the phase shift of the spectrum signal, the arithmetic controller 70 processes the A scan signal to obtain the depth position of the steady pattern noise, and obtains the phase information of the spectrum signal corresponding to the obtained depth position. The depth position of the steady pattern noise corresponds to the depth position of the interference component generated by the pattern noise generating member.

  More specifically, the arithmetic controller 70 detects the phase φ (Z0) of the spectrum signal at the FPN detection position based on F (Z0) at the depth position (FPN detection position) Z0 where the FPN is detected. May be. The phase φ (Z0) is a function with the horizontal axis: wavenumber k and the vertical axis: phase φ. For example, the phase φ (Z0) is obtained from Arc Tangent (inverse tangent) of the ratio of the real part RealF (Z0) and the imaginary part ImagF (Z0) of the Fourier transform value F (Z0) at the FPN detection position Z0. Here, the arc tangent of the ratio between the real part and the imaginary part of the Fourier transform value is calculated by Arc Tangent processing, and the phase φ is obtained.

  Next, the arithmetic controller 70, based on the acquired phase φ of the FPN detection position Z0, the Fourier transform value F of each A scan so that the phase shift (position shift amount) of the interference signal f (k) is removed. (Z) correction processing is performed (refer to Japanese Patent Application Laid-Open No. 2013-156229 for a detailed method of the above processing).

<Example>
In the following examples, the SS-OCT apparatus 1 shown in FIG. 1 is used as an optical coherence tomography apparatus, and the test object is the fundus of the eye.

  The SS-OCT apparatus 1 has a wavelength sweep type OCT (SS-OCT: Swept Source-OCT) as a basic configuration, a wavelength sweep light source (wavelength variable light source) 102, an interference optical system (OCT optical system) 100, and an arithmetic controller. (Arithmetic processor) 70 is mainly provided. In addition, the OCT apparatus 1 is provided with a memory 72, a monitor 75, a front image observation system and a fixation target projection system (not shown). An arithmetic controller (hereinafter, controller (control unit)) 70 is connected to the light source 102, the interference optical system 100, the memory 72, and the monitor 75.

  For the interference optical system 100, an SS-OCT (Swept Source-OCT) method is used. As the light source 102, a wavelength swept light source (wavelength scanning light source) is used. The light source 102 changes the emission wavelength at high speed in time.

  In the case of a wavelength swept light source, the light source 102 includes, for example, a laser medium, a resonator, and a wavelength selection filter. As the wavelength selection filter, for example, a filter using a combination of a diffraction grating and a polygon mirror or a Fabry-Perot etalon may be used.

  In this embodiment, a TUNABLE LASER manufactured by AXUN is used as a light source having a short instantaneous emission line width and a short resonator length (for example, λc = 1060 nm, Δλ = 110 nm, δλ = 0.055 nm, resonator length to 14 mm). Such a wavelength swept light source is described, for example, in US Publication No. 2009/0059971.

  The coupler (splitter) 104 divides the light emitted from the light source 102 into measurement light (measurement light) and reference light. The circulator 103 guides the light from the coupler 104 to the optical fiber 105 and guides the light from the optical fiber 105 to the optical fiber 119. The circulator 103 may be a coupler.

  The interference optical system 100 guides the measurement light to the fundus oculi Ef of the eye E by the measurement optical system 106. The interference optical system 100 guides reference light to the reference optical system 110. The interference signal light is acquired by interference between the measurement light reflected by the fundus oculi Ef and the reference light. The interference optical system 100 causes the detector (light receiving element) 120 to receive the acquired interference signal light.

  In the measurement optical system 106, an optical fiber 105, an optical scanner 108, and an objective lens system are sequentially provided. The measurement light travels to the optical scanner 108 via the circulator 103 and the optical fiber 105. The reflection direction of the measurement light is changed by the optical scanner 108. The light deflected by the optical scanner 108 becomes a parallel beam by the objective lens system, enters the eye E, and enters the fundus oculi Ef.

  The optical scanner 108 scans the measurement light in the XY direction (transverse direction) on the fundus oculi Ef. The optical scanner 108 is arranged at a position substantially conjugate with the pupil. The optical scanner 108 is, for example, two galvanometer mirrors, and the reflection angle thereof is arbitrarily adjusted by a driving mechanism.

  The reflection (advance) direction of the light beam emitted from the light source 102 is changed and scanned in an arbitrary direction on the fundus. As the optical scanner 108, for example, an acousto-optic device (AOM) that changes the traveling (deflection) direction of light may be used in addition to a reflecting mirror (galvano mirror, polygon mirror, resonant scanner).

  The controller 70 controls the driving of the optical scanner 108 to scan the measurement light in a direction (transverse direction) perpendicular to the depth direction of the fundus oculi Ef. Backscattered light (reflected light) from the fundus oculi Ef of each measurement light reaches the beam splitter 350 through the objective lens system, the optical scanner 108, the optical fiber 105, the circulator 103, and the optical fiber 119. The backscattered light is combined with the reference light by the beam splitter 350 and interferes therewith.

  The reference optical system 110 generates reference light that is combined with reflected light acquired by reflection of measurement light at the fundus oculi Ef. The reference optical system 110 may be a Michelson type or a Mach-Zehnder type. In this embodiment, the reference optical system 110 is formed by a transmission optical system (for example, an optical fiber), and guides the light from the coupler 104 to the detector 120 by transmitting the light without returning. The reference optical system 110 may be formed by, for example, a reflection optical system (for example, a reference mirror), and may be returned to the coupler 104 by reflecting light from the coupler 104 by the reflection optical system and guided to the detector 120.

  This apparatus moves at least a part of the optical member arranged in the interference optical system 100 in the optical axis direction in order to adjust the optical path length difference between the measurement light and the reference light. For example, the reference optical system 110 has a configuration that adjusts the optical path length difference between the measurement light and the reference light by moving an optical member in the reference light path. A configuration for changing the optical path length difference may be arranged in the measurement optical path. For example, an optical member (for example, an end of an optical fiber) arranged in the measurement optical path is moved in the optical axis direction.

  The beam splitter 350 divides the interference signal light into a plurality (two in this embodiment). The cover glass 400 and the first detector 121a are disposed on one side of the optical path divided by the beam splitter 350, and the second detector 121b is disposed on the other side.

  The balanced detector 121 performs balanced detection by detecting the interference signal light split by the beam splitter 350 by the first detector 121a and the second detector 121b. The interference signal from the first detector 121a and the interference signal from the second detector 121b have a phase difference of 180 °. The balanced detector 121 includes a circuit that processes detection signals from the first detector 121a and the second detector 121b, and includes an interference signal from the first detector 121a and an inverted signal from the second detector 121b. By obtaining the difference from the interference signal, the DC (direct current) component can be suppressed.

  Each detector is, for example, a point sensor having only one light receiving unit, and for example, an avalanche photodiode is used. Each detector may be spaced apart from each other.

  One of the lights divided by the beam splitter 350 is received by the first detector 121a via the cover glass 400, the first optical fiber 131a, and the first condenser lens 132a. The other of the lights divided by the beam splitter 350 is received by the second detector 121b via the second optical fiber 131b and the second condenser lens 132b.

  The cover glass 400 is used as an optical member for generating calibration interference light by one of the lights divided by the beam splitter 350.

  The cover glass 400 has a known thickness d. The front surface and the rear surface of the cover glass 400 are arranged so as to intersect perpendicularly to the optical axis L3. The interference signal light that passes through the cover glass 400 is transmitted light that passes through the cover glass 400 as it is, and the inside that passes through the cover glass after being reflected 2n (n = 1, 2, 3,...) Times in the cover glass 400. Divided into reflected light (see FIG. 2). The transmitted light and the internally reflected light interfere with each other to generate interference light.

  The interference light generated by the cover glass 400 is detected as fixed pattern noise by the first detector 121a. The peak of light that has passed through the cover glass 400 as it is and the peak of light that has been reflected twice within the cover glass 400 and passed through the cover glass 400 are detected 2n times (2nd) apart from the thickness of the cover glass 400.

  In the above example, the cover glass 400 is disposed between the beam splitter 350 and the first detector 121a, but the cover glass 400 is disposed between the beam splitter 350 and the second detector 121b. May be.

  When deciding whether to arrange on either side of the first detector 121a or the second detector 121b, the cover glass 400 may be arranged on the side where much light is guided. When the light is split by the beam splitter 350 (or the coupler 450 described below), the light is not split 50:50, and the intensity balance may be deteriorated. Therefore, by arranging the cover glass on the side where much light is guided, the light is attenuated by the cover glass 140, and the intensity balance is reduced.

  The reason why the cover glass 400 is provided on one detector side of the balanced detector 121 and the cover glass is not provided on the other detector side of the balanced detector is that when the DC component is removed by the balanced detector 121, the cover glass is not provided. This is because the interference component due to the above remains in the detection signal. That is, when cover glasses having the same thickness are provided on both, the interference components of both are canceled out as DC components and removed from the detection signal, making calibration difficult. That is, the present inventors can include the interference component for calibration in the interference signal by causing light through the cover glass 400 to enter one of the first detector 121a and the second detector 121b. I found out.

  Note that the present invention is not limited to the above, and optical members having different thicknesses may be disposed on both of the balance detectors 121 so that different steady pattern noises are generated. In this case, signals of two frequencies are included in the interference signal as stationary pattern noise. For example, the calibration accuracy is improved by preferentially using the signal having the lower frequency, so that the correction accuracy is improved.

  In the present embodiment, the cover glass 400 is fixedly disposed in the optical path. However, the present invention is not limited to this, and the cover glass 400 can be inserted into and removed from the optical path and inserted into the optical path as necessary. May be.

  When the emission wavelength is changed by the light source 102, the corresponding interference signal light is received by the balance detector 121. As a result, the interference signal light at each wavelength is received by the balanced detector 121 as spectrum light. The first detector 121a and the second detector 121b detect the interference signal light at a preset constant sampling rate. Thereby, the number of sampling points corresponding to the sampling rate is set. Since the light source 102 changes the emission wavelength with time, each sampling point by the balance detector 121 has a paired relationship with each emission wavelength (wave number) of the light source 102. The interference signal at each wavelength output from the balanced detector 121 is taken into the controller 70 as a spectrum signal. A depth profile is formed based on the obtained spectral signal.

  The controller 70 controls driving of the optical scanner 108 and scans the measurement light on the fundus oculi Ef in the transverse direction. The controller 70 forms a fundus tomographic image by sequentially arranging the depth profiles at the respective scanning positions.

  Below, an example in the case of correct | amending the mapping state (wave number sampling mapping) of each wavelength component (wave number component) with respect to the sampling point p based on the calibration component by the cover glass 400 is shown.

As shown in FIG. 2, when the light for calibration passes through the cover glass 400, the first component E ₁ (transmitted light beam) passing through the cover glass 140 and the inside of the cover glass 400 twice. A plurality of lights including the reflected _second component E ₂ (light flux reflected once on the rear surface and reflected once on the front surface) are received by the first detector 121a.

  The spectrum signal obtained by the balance detector 121 has information on light for calibration interfered by the cover glass 400. It is assumed that the refractive index n and the thickness d of the cover glass 400 are known in advance. Note that the thickness d is narrower than the measurement range of the interference optical system 100 in the present embodiment.

  The wavelength λ of light from which the calibration light beam is detected by the balance detector 121 is expressed by the following equation (1).

  Here, it is assumed that C = D = 0 as the first approximation, and A = λ0 (center wavelength of the light source). Further, the value of B is determined so as to satisfy an assumed wavelength width (for example, a design value). Here, p is a sampling point (p) in the detector, and an intermediate value in the sampling range in one wavelength sweep is set to 0. For example, if the sampling number in the present embodiment is 2048 points, p takes a value from −1024 to 1023.

  Next, based on even padding (4 times in this embodiment) of zero padding data, the interference intensity I (k) is linearized so that the k space (k is the wave number) is equally spaced. ) By applying FFT (Fast Fourier Transform) relating to k to I (k), 2nd≡z (peak) is obtained from a peak corresponding to twice the optical thickness nd of the cover glass. Next, after extracting only the positive frequency component, IFFT (Inverse Fast Fourier Transform) is performed, and the phase φ (k) is obtained from the real part and the imaginary part.

The interference light received by the first detector 121a includes a first component E ₁ = E ₀ exp (ikz) that is transmitted through the cover glass 400 and a second phase that is delayed by the amount reflected twice by the cover glass 140. Since the interference is the component E ₂ = rE ₀ exp (ik (z + 2nd)) (r is the total reflectance of the cover glass), the intensity distribution I (k) is expressed by the following equation (2)

The phase φ (k) described above means that exp (ik2nd) is extracted from Equation (2) and its phase is obtained. If the wave number sampling mapping in the spectrum signal changed by the wavelength swept light source is perfect, the following equation (3)

However, if the wave number mapping is incomplete, it will not be a straight line.

  Here, z (peak) is obtained as follows. The interference component can be generalized as exp (ikz), and k and z have a relationship of kz = 2π. From this, z is the following equation (4), where N is the number of sampling points, and kmax and kmin are the maximum and minimum values of the k value detected at each sampling point.

Can be expressed as: I = 0, 1, 2,..., N / 2
Here, if an interference signal corresponding to z (peak) is detected at the i (peak) th sampling point, z (peak) is expressed by the following equation (5).

It can be expressed as.

  Since φ (k) should ideally be a straight line with slope z (peak) and intercept 0, assuming that the second-order and third-order nonlinear terms are σ, k is expressed by the following equation (6):

It is corrected. The corrected wavelength λ ′ is determined as λ ′ = 2π / k ′. Where σ is the following equation (7)

And the nonlinear term σ = b ₂ k ² + b ₃ k ³ when expanded.

FIG. 3 is a diagram schematically illustrating mapping of spectrum signals to be corrected by performing correction calculation. Further, the corrected values of φ (kmin) and φ (kmax) are within a predetermined allowable range (for example, about 1E- ⁵ ) from the ideal values z (peak) · kmin and z (peak) · kmax. If so, it is determined that it has converged. If this condition is not satisfied, the same calculation is repeated again using the above-mentioned corrected λ ′.

  Thus, the controller 70 obtains correction information from the spectrum signal obtained by the balance detector 121 by calculation, and stores the obtained correction information in the memory 72. As a result, the correspondence between each wavelength component detected by the balance detector 121 and each sampling point is obtained more accurately.

  The configuration as described above is advantageous because the wave number mapping in SS-OCT can be optimized with a simple device configuration without providing a complicated optical system and circuit system.

  In the above configuration, the interference signal light is divided by the beam splitter 350, but the present invention is not limited to this. For example, as shown in FIG. 4, the interference signal light may be divided by a coupler 450.

  In the case of two-channel detection, a cover glass 400 may be arranged on one detector side in each channel (see FIG. 5). Two-channel detection may be applied to, for example, polarization-sensitive SS-OCT (for details, refer to, for example, JP2013-148482A). In addition to polarization-sensitive SS-OCT, two-channel detection includes, for example, Dual Beam SS-OCT (OCT that images two regions on the fundus simultaneously), Dual Beam Doppler SS-OCT (Doppler signal with delay between beams) OCT), and Full Range SS-OCT using polarized light.

  For example, the vertical polarization detector (first channel) 121V performs balanced detection on the vertical polarization components divided by the polarization beam splitters 360 and 365 by the first light receiving element 121Va and the second light receiving element 121Vb. The horizontal polarization detector (second channel) 121H performs balanced detection of the horizontal polarization components divided by the polarization beam splitters 360 and 365 by the first light receiving element 121Ha and the second light receiving element 121Hb.

1 SS-OCT device 70 Arithmetic controller (arithmetic processor)
100 Interference optical system 100 (OCT optical system)
102 light source 121 balance detector 121a first detector 121b second detector 350 beam splitter 400 cover glass 450 coupler

Claims (4)

An SS-OCT optical system using a wavelength swept light source that temporally sweeps the emission wavelength is provided, and an interference signal between the measurement light and the reference light is sampled according to a change in the emission wavelength by the wavelength swept light source, and obtained by sampling. An optical coherence tomography device that obtains internal information of a test object based on interference signals at respective wavelengths,
An optical splitter that divides interference signal light generated by interference between the measurement light and the reference light into first interference signal light and second interference signal light having a phase difference with respect to the first interference signal light. When,
A first detector for detecting the first interference signal light; and a second detector for detecting the second interference signal light, the detection from the first detector and the second detector. A balanced detector for processing the signal for balanced detection;
A stationary pattern noise caused by either the first interference signal light or the second interference signal light is disposed between one of the first detector and the second detector and the optical splitter. An optical member for causing
Correction information for correcting the mapping state of the wave number component to each sampling point in the balanced detector is calculated based on the signal component corresponding to the stationary pattern noise included in the detection signal output from the balanced detector. Computing processing means to be obtained;
An optical coherence tomography apparatus comprising: The balanced detector is a first balanced detector,
Further, a third detector for detecting the first interference signal light and a fourth detector for detecting the second interference signal light are provided, and the third detector and the fourth detector A second balanced detector for processing the detected signal to perform balanced detection;
In order to generate stationary pattern noise caused by either the first interference signal light or the second interference signal light, which is disposed between one of the third detector and the fourth detector and the optical splitter. A second optical member of
With
The arithmetic processing means is further configured to calculate a wave number component for each sampling point in the second balanced detector based on a signal component corresponding to the stationary pattern noise included in the detection signal output from the second balanced detector. 2. The optical coherence tomography apparatus according to claim 1, wherein correction information for correcting the mapping state is obtained by calculation. The first detector and the third detector are vertical polarization detectors for detecting an interference signal at each wavelength having a vertical polarization component,
The second detector and the fourth detector are used as a horizontal polarization detector for detecting an interference signal at each wavelength having a horizontal polarization component,
3. The optical coherence tomography apparatus according to claim 2, wherein a polarization characteristic of the test object is obtained based on an interference signal at each wavelength having the vertical polarization component and the horizontal polarization component.   The arithmetic processing unit corrects a phase shift of a spectrum signal including an interference signal at each wavelength based on a signal component corresponding to the stationary pattern noise included in a detection signal output from the balanced detector. The optical coherence tomography apparatus according to any one of claims 1 to 3.